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Narrower arc from blunt tungsten

A fellow on Welding Web (I think he's in witness protection so I won't name him) posted a chart of tungsten shapes, and how they relate to arc width and penetration (or lack of it). The chart is without explanatory information. I don't know if AC, DC or if it matters.
It shows that a very blunt grind produces a pinpoint arc, while a needle like grind produces a wide arc with little penetration. I've been grinding to a needle point trying to focus the arc. It seems that was the wrong thing to do.
We have discussed why, My uninformed guess has to do with the surface current phenomenon and the fact that electrons seek to continue running straight. A current on a cylindrical object will be concentrated on the surface. This higher current will tend to steer the rest of the current. As the shoulder of the grind is farther away from the work piece arc will originate farther away, if from a long pointed tungsten. From a shorter point it will be easier for current to continue along its "current" path, ionizing, then arcing across the gap.

I'm guessing here. Is there merit to my theory, or are other forces at play?

A fellow on Welding Web (I think he's in witness protection so I won't name him) posted a chart of tungsten shapes, and how they relate to arc width and penetration (or lack of it). The chart is without explanatory information. I don't know if AC, DC or if it matters.
It shows that a very blunt grind produces a pinpoint arc, while a needle like grind produces a wide arc with little penetration. I've been grinding to a needle point trying to focus the arc. It seems that was the wrong thing to do.
We have discussed why, My uninformed guess has to do with the surface current phenomenon and the fact that electrons seek to continue running straight. A current on a cylindrical object will be concentrated on the surface. This higher current will tend to steer the rest of the current. As the shoulder of the grind is farther away from the work piece arc will originate farther away, if from a long pointed tungsten. From a shorter point it will be easier for current to continue along its "current" path, ionizing, then arcing across the gap.

I'm guessing here. Is there merit to my theory, or are other forces at play?

Diamond Ground products shows the same information. I don't remember if they gave an explanation.

No, I tried to copy and paste, no such luck. It came with no text, a series of black and white photographs of arc shapes at 200 amps. Scale is not specified, it appears to be 1/8" tungsten. They show arc, and cut and etched weld. Using a large variety of incrementally long points including square cut. The trend shows deep penetration, and narrow arc, and bead from blunt ground tungsten, and wide arc, shallow penetration from long pointed tungsten.

I've been grinding long points in an effort to narrow bead width in aluminum, envisioning it delivering a pinpoint arc that would minimize the size of the heat affected zone. If this new information is good, I can narrow the heat affected zone with a blunt "golf pencil point".

In the photos arc appears to originate from the shoulder where the tungsten begins to narrow, flaring out from there. In the extremely blunt grinds or balled from cylinder, arc appears to blow straight off the end of the tungsten.

The explanation as I recall is that the electrons tend to be admitted from the tungsten at a 90 degree angle to the surface of the tungsten. They then are curved towards the weldment by the electric field. If the electrode is ground to a very narrow angle the electrons are emitted almost sideways and thus require more time and effort to be pulled to the weldment. This allows them to move further from the electrode and thus a wider arc. If the electrode is blunt, an unsharpened electrode being the extreme case, they are already "aimed" more towards the weldment and thus produce a narrower arc.

Think of firing a shotgun at various angles from horizontal to vertical and envision where the pellets will land. Sort of the same concept.

Narrower arc from blunt tungsten

Had small amount of steel Tig on Friday. Tried blunt tungsten as similar to what is du for Alm.
Can't say as this small test that I agree.
I've always sharpened to point for steel & just didn't seem as good with blunt style grind. My arc seemed wider & less penetration than with pencil sharp grind. But was small amount of welding so not fair test but not so sure I like it as well. Will try again next week.
Greg